Investors can choose from literally thousands of exchange-traded funds (ETFs), which means picking the best ETFs can be daunting.

More than a dozen funds track well-known basic indexes such as the Standard & Poor's 500-stock index, Dow Jones Industrial Average and Russell 2000. Scores of other ETFs try to beat those benchmarks by carving out certain types of stocks or bonds, or by emphasizing things such as value or share-price momentum - anything to give them an edge.

We've picked The Kiplinger ETF 20 with an eye toward low fees, making this a list of the 20 best cheap ETFs to use to reach your investing goals. Our selections will give you anything from broad market exposure to narrow tactics meant to help you fill specific gaps in your portfolio. Read on to learn about these 20 ETF picks.

iShares Core S&P 500

Market value: $166.4 billion

Yield: 1.7%

Expense ratio: 0.04%, or $4 per $10,000 invested

Trades commission-free at: Fidelity, Firstrade, Vanguard

Standard & Poor's 500-stock index is synonymous with the U.S. market and is the benchmark against which most large-cap managers are judged. Stocks such as Exxon Mobil (XOM), Apple (AAPL) and Bank of America (BAC) dot its holdings.

All three S&P 500-tracking funds easily rank as cheap ETFs. But the iShares Core S&P 500 (IVV, $294.47) has a key structural advantage. The classic S&P 500 index ETF - the SPDR S&P 500 ETF Trust (SPY) - is structured as a unit investment trust. As such, dividends from the SPY's underlying holdings must be held as cash until they are distributed to shareholders. As an ETF, IVV can immediately reinvest its dividends, improving its return.

iShares Core S&P Mid-Cap

iShares Core S&P Mid-Cap (IJH, $203.36) is the best pure play on midsize-company stocks, which offer almost all of the advantages of small caps but with much less risk, yet also boast more upside than many large-cap stocks.

According to data provided by the Schwartz Investment Counsel, a $1,000 investment made in the S&P MidCap 400 Index on March 1, 1984, would have been worth $74,159 at the end of the first quarter of 2018. For comparison's sake, the same $1,000 investment made in large caps and small caps, respectively, would be worth only $38,155 and $31,567.

Standard and Poor's excludes financially weak midcaps from this index - a culling that has enabled the index to outperform other midcap indexes over the past 10 years.

Vanguard FTSE All-World ex-US Small Cap

Vanguard FTSE All-World ex-US Small-Cap (VSS, $113.35) tracks an index of about 3,460 small- and medium-capitalization stocks in both developed and emerging markets.

Small-cap stocks tend to be riskier than large caps. But this ETF hasn't been much more volatile than its large-cap counterpart. And it has edged foreign large caps over the past three years by an average of 0.9 percentage points per year.

The biggest chunk of VSS' holdings (37.8%) are European developed-country stocks, with another 28.8% in developed Pacific countries and another 12.9% in developed North America. The vast majority of the remainder is invested in emerging markets.

Vanguard Russell 2000 Value

Although value stocks are always, by definition, cheaper than growth stocks, the valuation gap between the two is among the largest it has been since 1942. Value stocks tend to beat growth stocks when they are this cheap, making Vanguard Russell 2000 Value (VTWV, $116.94) more compelling than a broad small-cap fund.

At the moment, top holdings include the likes of Idaho utility Idacorp (IDA), Louisiana-based regional bank IberiaBank (IBKC) and LED specialist Cree Inc. (CREE).

Vanguard Total International Stock

Vanguard Total International Stock (VXUS, $54.38), which holds some 6,000 stocks, is one of the cheapest ETFs to deliver stock exposure outside the U.S. Because it weights stocks by market value, the biggest companies dominate the fund; the median market value of its holdings is $24 billion.

Overall, the fund has about 83% of its assets in developed markets, led by Japan at 17%. Emerging markets rounded out the total, with 19% in countries such as China, India and South Korea.

Vanguard Total Stock Market

Vanguard Total Stock Market (VTI, $150.61) gives you the entire U.S. stock market - large, midsize and - small companies. The fund tracks the CRSP U.S. Total Market Index, which includes some 3,600 stocks - making it much broader than the S&P 500.

Still, large companies dominate the index, and the fund's return rarely deviates from the S&P by more than 1 percentage point or so in any calendar year.

Schwab US Dividend Equity

Schwab US Dividend Equity (SCHD, $53.71) invests only in companies that have paid dividends every year for at least 10 years, that boast a market value of at least $500 million, and whose stocks have significant daily trading volume. Finally, only those companies with the best relative financial strength - as measured by four factors, including return on equity and five-year dividend growth rate - make the cut.

That leads to a portfolio of 120-plus stocks, led by the likes of Intel (INTC), Exxon and Pfizer (PFE).

Vanguard Dividend Appreciation

Vanguard Dividend Appreciation (VIG, $111.66) is more concerned with whether a company has consistently boosted its annual dividend than about the size of the payout. Vanguard Dividend Appreciation tracks an index of large companies that have raised their annual payouts for at least the past 10 consecutive years. Limited partnerships, real estate investment trusts (REITs) and financially troubled companies are not eligible for the ETF.

The result is 182 mostly large U.S. firms in a mix of industries, with the stocks weighted in the fund by market value. The fund rebalances once a month, as does the index it tracks. Its top three holdings are Microsoft (MSFT), Johnson & Johnson (JNJ) and Walmart (WMT).

The fund's focus on growth, says Morningstar analyst Adam McCullough, results in a higher-quality portfolio. "It reduces the fund's exposure to firms that may not be able to sustain their dividend payments, which is a risk that often accompanies a narrow focus on yield," he says."

WisdomTree Global ex-US Quality Dividend Growth

WisdomTree Global ex-US Quality Dividend Growth's (DNL, $57.79) name suggests that it invests in international companies that increase their dividends - and ultimately, it does. But it takes a winding path to get there.

The fund invests in growing, high-quality dividend-paying firms in emerging and developed countries. The quality screen sorts companies by their historical return on equity and return on assets (both are measures of profitability). The growth screen zooms in on three- to five-year earnings growth expectations. "We created the same quality and growth screens that Warren Buffett likes," says Jeremy Schwartz, of WisdomTree.

Stocks in the fund are weighted by their share of the dividend stream of the index - the more they contribute, the bigger their share of the fund's assets. The rationale is that efficiently run firms with increasing earnings will likely raise dividends over time and have stocks that perform well, too.

Fidelity MSCI Industrials Index

Fidelity MSCI Industrials Index (FIDU, $40.41) is among the best cheap ETFs for single-sector exposure. It tracks an index of 341 industrial companies, in businesses ranging from construction equipment and factory machinery makers to aerospace and transportation businesses. These companies tend to see sales rise in a strong economy and slump when growth slows, making them good bets now.

The fund currently emphasizes giants such as Boeing (BA), 3M (MMM) and Honeywell (HON). These firms generate much of their sales overseas and would benefit from strong economic growth abroad and a weaker U.S. dollar, which also makes profits earned in foreign currencies worth more when converted to greenbacks.

About one-third of FIDU consists of small and midsize stocks. Smaller companies provide more exposure to sub-industries - such as electrical equipment, construction and engineering - and that adds to the fund's diversification. The fund's annual expense ratio of 0.08% is lower than that of any other industrials ETF.

Financial Select Sector SPDR

Financial Select Sector SPDR (XLF, $28.42) holds commercial banks such as JPMorgan (JPM) and Wells Fargo (WFC) as well as insurers, financial-services firms and investment banks - a sector that's sensitive to changes politicians in Washington might make to both regulations and interest rates.

But its top holding is Berkshire Hathaway (BRK.B), run by Warren Buffett. Although Berkshire's big insurance unit gives it a lot of financial exposure, the company has stakes in everything from food products to railroads. No matter how the political winds blow in Washington, Berkshire should thrive.

Invesco Dynamic Large Cap Value

Invesco Dynamic Large Cap Value (PWV, $37.87) tracks an enhanced index of undervalued stocks. Stocks in the ETF rank strongly on measures such as earnings momentum, balance-sheet strength and a history of raising dividends. The highest-scoring stocks get the most weight. The result is a collection of 50 stocks that looks somewhat different from the fund's bogey, the Russell 1000 Value index. The ETF's top 10 holdings include Qualcomm (QCOM), Illinois Tool Works (ITW) and T-Mobile US (TMUS), none of which crack the Russell index's top 10.

PowerShares rejiggers the holdings every three months to reflect changes in scores. One downside of all this activity: Annual fees are relatively steep for an ETF.

Invesco S&P 500 Equal Weight Health Care

If you want the long-term growth of health-care stocks but worry about a rough landing for high-flying biotech stocks, look no further. Invesco S&P 500 Equal Weight Health Care (RYH, $203.40) takes the 61 health-care stocks in the S&P 500 and weights them equally. Thus, stocks such as PerkinElmer (PKI) and HCA Healthcare (HCA) have just as much say in the company's performance as companies such as Pfizer and CVS Health (CVS).

Biotech stocks represent 16% of the fund's assets, compared with 38% in the typical health-care ETF.

iShares Edge MSCI USA Momentum Factor

iShares Edge MSCI USA Momentum Factor (MTUM, $118.56) holds a big slug of tech - about 41% at the moment. But it holds an array of other stocks with good price momentum, including in consumer discretionary (~20%) and financials (~12%).

If technology stocks keep surging, this cheap ETF's aggression will benefit. But the fund won't lose as much as a pure tech ETF if the sector fizzles out.

Pimco Active Bond

PIMCO Active Bond (BOND, $102.31) is, as its name suggests, an actively managed ETF (most ETFs merely seek to match an index). The ETF is run like Pimco's flagship mutual fund, Pimco Total Return (PTTDX). It's on this list of the best cheap ETFs because of its relatively low expenses - relative to other active bond offerings.

The fund holds $2.1 billion in assets; the mutual fund, which was once the biggest in the land, contains $73 billion.

Pimco has seen a good bit of turmoil in past years with the resignation of co-founder Bill Gross, but we think the firm still has a lot of talent.

SPDR DoubleLine Total Return Tactical

We're fans of Jeffrey Gundlach, a comanager of this actively managed ETF with Philip Barach and Jeffrey Sherman. He and Barach also run DoubleLine Total Return Bond (DLTNX), which is a member of the Kiplinger 25, the list of our favorite no-load mutual funds - although the fund and the ETF are not clones.

SPDR DoubleLine Total Return Tactical (TOTL, $47.11) draws on the view of Gundlach and his asset allocation team on the global economy and world markets. The ETF currently invests mostly in bonds with credit ratings of BBB or better that it deems attractively priced.

But almost anything goes. The fund can invest in corporate debt, government bonds, floating-rate securities, foreign corporate and government IOUs, and Gundlach's bailiwick - mortgage-backed and asset-backed securities. There are some guard rails. No more than 25% of the ETF's net assets can be invested in high-yield debt, and no more than 15% in foreign-currency-denominated securities. But there is no cap on mortgage-backed securities. At last report, the fund had 52.8% of its assets invested in MBSes and 16.2% in Treasuries.

DoubleLine Total Return Tactical yields 3.4% and its duration is 4.7 years, implying that if rates were to fall by 1 percentage point, the fund's net asset value would drop 4.7%.

Invesco Senior Loan Portfolio

Invesco Senior Loan Portfolio (BKLN, $23.11) holds loans made by banks to heavily indebted firms with poor credit ratings. These junk-rated borrowers are charged "floating" interest rates that are typically tied to a short-term benchmark: the London Interbank Offered Rate, or LIBOR.

When LIBOR rises above a certain level, rates on these loans bump up, helping them hold their value better than bonds.

Pimco Enhanced Low Duration Active

We're adding Pimco Enhanced Low Duration Active (LDUR, $99.58) to the Kip ETF 20 roster as a defense against rising rates. The managers behind the fund - Hozef Arif, David Braun and Jerome Schneider - are Pimco veterans. Their goal is to keep the portfolio's sensitivity to interest-rate moves low.

The ETF currently has a 1.52-year duration. That implies that if interest rates overall were to rise by 1 percentage point, the fund's net asset value would drop by roughly 1.5%. Compare that with the nearly 6-year duration of the broad bond market bogey, the aforementioned Agg index.

The fund's yield is boosted in part by investment-grade corporate debt, mortgage-backed securities and a smattering of exposure to emerging-markets and high-yield corporate debt.

VanEck Vectors Fallen Angel High Yield Bond

VanEck Vectors Fallen Angel High Yield Bond (ANGL, $29.00) holds IOUs originally issued with investment-grade ratings but subsequently downgraded to junk status. If issuers of these "fallen angels" can recoup their investment-grade status, which happens on occasion, the bonds should rally, supplementing the fund's considerable interest income.

Top holdings at the moment include bonds from companies such as Sprint (S), EMC Corp. (EMC) and Freeport-McMoRan (FCX).

Vangaurd Total International Bond

Vangaurd Total International Bond (BNDX, $54.50) tracks an index of foreign bonds. But despite its name, this cheap bond ETF doesn't invest in every international debt security. Rather, the fund focuses on high-quality, investment-grade bonds. The portfolio is filled primarily with government and quasi-government debt issued mostly in developed countries (though 3.9% of the portfolio's assets are in emerging-markets debt, at last report).

Because the fund holds bonds issued in local currencies, not U.S. dollars, Total International Bond hedges against currency risk, which sets it apart from many world bond funds. Hedging "smooths the ride," says Wyatt Lee, of T. Rowe Price Group, who notes that "Currency (fluctuations) can double the volatility of a global bond fund."

The caveat is the fund's nearly 8-year duration, implying an 8% decline in net asset value for every one-point rise in rates. Although interest rates abroad are currently low and expected to stay that way for the time being - especially in Japan and Europe, where much of the fund's assets are invested - when interest rates eventually rise, it could crimp returns.

We'll be keeping an eye on that.

Nellie S. Huang is a Senior Associate Editor at Kiplinger's Personal Finance. Kyle Woodley is a Senior Investing Editor at Kiplinger.